6.15-stable review patch. If anyone has any objections, please let me know.
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From: Jocelyn Falempe jfalempe@redhat.com
[ Upstream commit 675008f196ca5c8d8413204e861cc2a2238581aa ]
On 32bits ARM, u64/u64 is not supported [1], so change the algorithm to use a simple fifo with decimal digits as u8 instead. This is slower but should compile on all architecture.
Link: https://lore.kernel.org/dri-devel/CANiq72ke45eOwckMhWHvmwxc03dxr4rnxxKvx+HvW... [1] Reported-by: Miguel Ojeda ojeda@kernel.org Closes: https://lore.kernel.org/dri-devel/CANiq72ke45eOwckMhWHvmwxc03dxr4rnxxKvx+HvW... Fixes: ccb8ce526807 ("ARM: 9441/1: rust: Enable Rust support for ARMv7") Signed-off-by: Jocelyn Falempe jfalempe@redhat.com Link: https://lore.kernel.org/r/20250418165059.560503-1-jfalempe@redhat.com Acked-by: Javier Martinez Canillas javierm@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/drm_panic_qr.rs | 71 ++++++++++++++++++++++----------- 1 file changed, 48 insertions(+), 23 deletions(-)
diff --git a/drivers/gpu/drm/drm_panic_qr.rs b/drivers/gpu/drm/drm_panic_qr.rs index ba6724aed51c9..de2ddf5dbbd3f 100644 --- a/drivers/gpu/drm/drm_panic_qr.rs +++ b/drivers/gpu/drm/drm_panic_qr.rs @@ -366,8 +366,48 @@ impl Segment<'_> { SegmentIterator { segment: self, offset: 0, - carry: 0, - carry_len: 0, + decfifo: Default::default(), + } + } +} + +/// Max fifo size is 17 (max push) + 2 (max remaining) +const MAX_FIFO_SIZE: usize = 19; + +/// A simple Decimal digit FIFO +#[derive(Default)] +struct DecFifo { + decimals: [u8; MAX_FIFO_SIZE], + len: usize, +} + +impl DecFifo { + fn push(&mut self, data: u64, len: usize) { + let mut chunk = data; + for i in (0..self.len).rev() { + self.decimals[i + len] = self.decimals[i]; + } + for i in 0..len { + self.decimals[i] = (chunk % 10) as u8; + chunk /= 10; + } + self.len += len; + } + + /// Pop 3 decimal digits from the FIFO + fn pop3(&mut self) -> Option<(u16, usize)> { + if self.len == 0 { + None + } else { + let poplen = 3.min(self.len); + self.len -= poplen; + let mut out = 0; + let mut exp = 1; + for i in 0..poplen { + out += self.decimals[self.len + i] as u16 * exp; + exp *= 10; + } + Some((out, NUM_CHARS_BITS[poplen])) } } } @@ -375,8 +415,7 @@ impl Segment<'_> { struct SegmentIterator<'a> { segment: &'a Segment<'a>, offset: usize, - carry: u64, - carry_len: usize, + decfifo: DecFifo, }
impl Iterator for SegmentIterator<'_> { @@ -394,31 +433,17 @@ impl Iterator for SegmentIterator<'_> { } } Segment::Numeric(data) => { - if self.carry_len < 3 && self.offset < data.len() { - // If there are less than 3 decimal digits in the carry, - // take the next 7 bytes of input, and add them to the carry. + if self.decfifo.len < 3 && self.offset < data.len() { + // If there are less than 3 decimal digits in the fifo, + // take the next 7 bytes of input, and push them to the fifo. let mut buf = [0u8; 8]; let len = 7.min(data.len() - self.offset); buf[..len].copy_from_slice(&data[self.offset..self.offset + len]); let chunk = u64::from_le_bytes(buf); - let pow = u64::pow(10, BYTES_TO_DIGITS[len] as u32); - self.carry = chunk + self.carry * pow; + self.decfifo.push(chunk, BYTES_TO_DIGITS[len]); self.offset += len; - self.carry_len += BYTES_TO_DIGITS[len]; - } - match self.carry_len { - 0 => None, - len => { - // take the next 3 decimal digits of the carry - // and return 10bits of numeric data. - let out_len = 3.min(len); - self.carry_len -= out_len; - let pow = u64::pow(10, self.carry_len as u32); - let out = (self.carry / pow) as u16; - self.carry %= pow; - Some((out, NUM_CHARS_BITS[out_len])) - } } + self.decfifo.pop3() } } }